The Mean Magnetic Field Strength of CI Tau

TL;DR

This study measures the mean magnetic field strength of the young star CI Tau using near-infrared spectral analysis, finding a consistent value around 2.2 kG and suggesting a possible temperature-magnetic field trend among T Tauri stars.

Contribution

It provides the first magnetic field measurement for CI Tau using near-infrared Zeeman broadening and compares two different modeling approaches for consistency.

Findings

Mean magnetic field strength of CI Tau is approximately 2.2 kG.

Consistent results from two modeling methods.

Potential correlation between stellar temperature and magnetic field strength.

Abstract

We present a blind comparison of two methods to measure the mean surface magnetic field strength of the classical T Tauri star CI Tau based on Zeeman broadening of sensitive spectral lines. Our approach takes advantage of the greater Zeeman broadening at near-infrared compared to optical wavelengths. We analyze a high signal-to-noise, high spectral resolution spectrum from 1.5-2.5um observed with IGRINS (Immersion GRating INfrared Spectrometer) on the Discovery Channel Telescope. Both stellar parameterization with MoogStokes (which assumes an uniform magnetic field) and modeling with SYNTHMAG (which includes a distribution of magnetic field strengths) yield consistent measurements for the mean magnetic field strength of CI Tau is B of ~2.2 kG. This value is typical compared with measurements for other young T Tauri stars and provides an important contribution to the existing sample given it is the only known developed planetary system hosted by a young classical T Tauri star. Moreover, we potentially identify an interesting and suggestive trend when plotting the effective temperature and the mean magnetic field strength of T Tauri stars. While a larger sample is needed for confirmation, this trend appears only for a subset of the sample, which may have implications regarding the magnetic field generation.